1. Field of the Invention
The present invention relates to a composition for external application having an excellent skin lightening and whitening effect.
2. Prior Art
Although there are many unclear points about development of pigmentation such as smear or freckle in human skin, it has been generally considered that stimulus due to hormone abnormality or UV radiation produces an excess amount of melanin, thereby causing undesired melanism in human skin.
In order to prevent or improve such a pigmentation, there have hitherto been used cosmetics having a lightening and whitening effect and containing, as effective components, peroxides such as hydrogen peroxide, zinc peroxide and magnesium peroxide, ascorbic acid, glutathione, colloidal sulfur, and various natural substances. However, many of these effective components has caused problems concerning safety, stability or smell. Besides, the effects of these components are not necessarily satisfactory.
Further, hydroquinone has been used as a skin-decoloring agent in U.S.A., etc. However, hydroquinone has irritating property and allergic property, thereby causing a problem concerning safety when the hydroquinone is used as effective component of cosmetics.
Accordingly, various studies has been made to develop cosmetics capable of exhibiting skin lightening and whitening effects without the afore-mentioned drawbacks. There have been proposed lightening and whitening agents for external application using kojic acid and kojic acid derivatives (Japanese Patent Unexamined Publication (KOKAI) No. 3538/1978, and Japanese Patent Examined Publications (KOKOKU) Nos. 18569/1981, 22151/1983, 9722/1985 and 60801/1986), cosmetics containing quercetin as effective components (Japanese Patent Unexamined Publication (KOKAI) No. 92305/1980), cosmetics containing fatty acid esters of quercetin as an effective component (Japanese Patent Unexamined Publication (KOKAI) No. 131911/1983), cosmetics containing catechin, etc., as effective components (Japanese Patent Unexamined Publication (KOKAI) No. 44375/1977), or the like. However, in practical use, these cosmetics have caused problems that the lightening and whitening components have still insufficient stability and therefore cannot exhibit a sufficient effect on human beings though their effects at the cell level are noticeable.
Under these circumstances, in order to provide agents for external application which are free from the afore-mentioned problems and excellent in skin lightening and whitening effect, and further do not cause problems concerning stability and smell, the present inventors have previously proposed the use of ellagic acid-based compounds or alkali metal salts of the ellagic acid-based compounds (Japanese Patent No. 1839986).
However, further studies made by the present inventors have revealed that in the case where the afore-mentioned ellagic acid-based compounds or alkali metal salts of the ellagic acid-based compounds are added into a base of cosmetics or quasi-drugs, the resultant agents have a low percutaneous absorption property and therefore cannot exhibit satisfactory effects even though these agents are blended at the concentration adopted for ordinary agents for external application.